Synthesis and characterization of poly(d,l-lactic acid) via enzymatic ring opening polymerization by using free and immobilized lipase

Polylactic acid is an interesting biodegradable and bioabsorbable material, and is produced from lactic acid, either by the direct polycondensation of lactic acid or via the ring-opening polymerization (ROP) of lactide. A future target of it is to improve some of the polyester properties for specific biomedical applications. The biocatalytic ROP of lactide is attractive as a route to polymer synthesis due to its lack of toxic reactants, mild reaction requirements, and recyclability of immobilized enzyme. Therefore, the use of immobilized enzymes is also being investigated. The aim of this work was to develop a methodology to synthesize high molecular weight polylactic acid via enzymatic ROP method using free enzyme and Candida antarctica lipase B (CALB) immobilized onto chitin and chitosan. The efficiency of the two approaches has been compared, with polymerization kinetics and resulting products fully characterized by FT-IR, NMR, DSC, XRD, and TGA analyses.